It’s the developed world’s drug of choice, and is also one of the few supplements that isn’t snake oil. Caffeine won’t raise your metabolic output to any notable degree, except within it’s initial week or so of use, but what it can do is suppress appetite. It also can increase your physiological and mental capacity.
Caffeine use is a mixed bag and is not for everyone, but it can help. See examine.com’s research summary of caffeine for a full breakdown of what the available scientific research says about regular caffeine use.